Influence of glacial influx on the hydrodynamics of Admiralty Bay,
Antarctica - a case study based on combined hydrographic measurements
and numerical modeling
Abstract
This study investigates the impact of glacial water discharges on the
hydrodynamics of Admiralty Bay (AB) in the South Shetland Islands, a
wide bay adjacent to twenty marine-terminating glaciers. From December
2018 until February 2023, AB water properties were measured on 136 days.
This dataset showed that a maximally two-layered stratification occurs
in AB, and that glacial water is always the most buoyant water mass.
Using the Delft3D Flow, a three-dimensional hydrodynamical model of AB
was developed. During tests, the vertical position and initial velocity
of glacial discharges have been shown to be insignificant for the
overall bay circulation. Fourteen model scenarios have been calculated
with an increasing glacial influx added. The AB general circulation
pattern consists of two cyclonic cells. Even in scenarios with
significant glacial input, water level shifts and circulation are
predominantly controlled by the ocean. Glacial freshwater is carried out
of AB along its eastern boundary in a surface layer no thicker than 60
m. Within the inner AB inlets, significant glacial influx produces
buoyancy-driven vertical circulation. Using an innovative approach
combining hydrographic and modeling data, a four-year, unprecedentedly
high-resolution timeseries of glacial influx volumes into AB has been
produced. On average, glacial influx summer values are >10
times greater than in spring and winter and 3 times higher than in
autumn. The annual glacial influx into AB was estimated at 0.525 Gt.
Overall, it was demonstrated how the topography and forcing controlling
the hydrodynamics of an Antarctic bay differs from that of well-studied
northern-hemisphere fjords.